Thermoplastic resins have a lower specific gravity than glass or metal and superior properties such as moldability and impact resistance. Plastic resins have been widely used in various products, such as electrical/electronic appliances and automobile components as a substitute for glass or metal in order to reduce costs, facilitate mass production and decrease weight. Accordingly, function as exterior materials and appearance of thermoplastic resins become important, and requirements for external impact and scratch resistance are increasing.
Polycarbonate based thermoplastic resins among thermoplastic resins have superior impact strength, heat resistance and transparency, and thus are used in a variety of engineering equipment.
However, polycarbonate based thermoplastic resins have relatively poor fluidity. Accordingly, in order to enhance fluidity of polycarbonate based thermoplastic resins, a mixture comprising one or more polymer and additives is used.
Conventionally, in order to enhance fluidity of polycarbonate based thermoplastic resins, a styrene-acrylonitrile (SAN) resin having a low molecular weight have been tried. However, fluidity was successfully enhanced, but impact strength and heat resistance were decreased.
In addition, in conventional PC/SAN alloy technology, g-ABS as an impact modifier was used. Since g-ABS has high affinity to SAN, g-ABS is present within SAN upon alloying PC/SAN (alloy), and, when external impact is applied, an interface between PC and SAN is firstly, mainly destroyed, thereby decreasing impact reinforcing effects. Accordingly, when g-ABS is used as an impact modifier, an interface between PC and SAN is firstly, mainly destroyed upon external impact.
Accordingly, the present inventors tried to enhance impact reinforcing effects by using a rubber-modified acrylic graft copolymer resin having affinity similar to PC and SAN. In addition, the present inventors tried to develop a polycarbonate based thermoplastic resin composition having enhanced moldability and processability due to superior fluidity, without decrease of mechanical properties such as impact strength and heat resistance.